import math
x1,y1,x2,y2=map(float,raw_input().split())
print "%.5f"%(float(math.sqrt((x1-x2)**2+(y1-y2)**2))) import math math x1,y1,x2,y2=map(float,raw_input().split()) x1 map(float,raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 print "%.5f"%(float(math.sqrt((x1-x2)**2+(y1-y2)**2))) "%.5f" float(math.sqrt((x1-x2)**2+(y1-y2)**2)) float math.sqrt((x1-x2)**2+(y1-y2)**2) math.sqrt math sqrt (x1-x2)**2+(y1-y2)**2 (x1-x2)**2 x1-x2 x1 x2 2 (y1-y2)**2 y1-y2 y1 y2 2 x2,y2=map(float,raw_input().split()) map(float,raw_input().split()) x2 x1,y1,x2,y2=map(float,raw_input().split()) map(float,raw_input().split()) x1 y1,x2,y2=map(float,raw_input().split()) map(float,raw_input().split()) y1 y2=map(float,raw_input().split()) map(float,raw_input().split()) y2
import math
x1,y1,x2,y2=map(float,raw_input().split())
print "%.5f"%(float(math.sqrt((x1-x2)**2+(y1-y2)**2)))